1. Field of the Invention
This invention relates to a pointer mechanism, which is suitable for a push-button tuner, etc., specifically to an improvement of an adjustable pointer mechanism.
2. Description of the Prior Art
Generally, for a push-button tuner, an indicator is provided to display a tuning frequency selected by manipulating one of the push-buttons. This indicator displays mechanically the tuning frequency and is so constructed that its pointer indicates correctly the position on a scale in frequency by selection of a broadcast station by turning a manual tuning dial or by pressing a desired button.
An example of this type of indicator is shown in FIG. 1. An upper plate 2 is disposed on the push-buttons 1. On this upper plate 2 are disposed a bar-shaped link 3, a chevron-shaped link 4 and a T-shaped pointer board 5, which are mutually coupled. That is, an extremity of the bar-shaped link 3 is coupled by a coupling pin 20 with the upper plate 2, and the other extremity of the bar-shaped link 3 is coupled by a coupling pin 21 with an extremity of the horizontal member of the T-shaped pointer board 5. On the other hand, the other extremity of the horizontal member of the T-shaped pointer board 5 is coupled by a coupling pin 22 with an extremity of the chevron-shaped link 4 and the other extremity of the chevron-shaped link 4 is coupled with a core slide 23, which in turn is linked with the dial or the push-buttons.
In a push-button tuner, movements of a dial or a push-button are thus transformed, by a well-known manner, through the bar-shaped link 3 and the chevron-shaped link 4 into deviations right or left of the pointer board 5, and the pointer at the extremity of this pointer board 5 indicates a selected frequency. Consequently, when the links 3 and 4 and the pointer board 5 are mounted, tolerances and fluctuations in length of each part, diameters of the coupling pins and the coupling holes, into which the pins are inserted, as well as displacement strokes of the core slide etc. for moving the pointer, give rise to errors or incorrectness in position of the extremity of the pointer board, and it is necessary to read just the position of the pointer during the last fabrication step.
Heretofore, bending of the plate of the pointer board 5 (plastic deformation) has been utilized as adjusting means of the pointer. That is, the T-shaped pointer board 5 is made of a metallic plate, which is provided with notches 6 at both sides, and a pointer 7 is fixed at an extremity of the pointer board 5 so as to protrude upwardly. In order to adjust the position of the pointer of such a conventional indicator, the pointer has been displaced at a desired position by bending right or left the pointer board 5 at a portion having notches 6.
However, for this conventional type of indicator, the pointer 7 thus adjusted is, as shown in FIG. 2, retreated back by .DELTA.l with respect to its original position. Moreover, the pointer 7 becomes more distant from the scale board by this adjustment and this gives rise to errors in frequency indication of the pointer, depending upon the position of the eyes of the observer. For these reasons this conventional type of indicator had a disadvantage that correct indication in frequency was difficult. Furthermore, since it was bending of a metallic plate that was utilized for adjustment, the number of adjustments of the pointer was restricted. Therefore, it was also a disadvantage that the pointer was easily broken at the portion having the notches 6, when readjustment was repeated several times. Moreover, the distance between the pointer 7 and the notches should be so long that the indicator is easily readjusted by bending of the pointer board at the portion having the notches 6 and has a predetermined large range of adjustment. This length necessitates inevitably that the pointer board has certain large dimensions, what influences the largeness of the whole tuner and prevents reduction in size of the tuner. Further, there was another disadvantage that, since the metallic plate of the pointer board becomes thinner and thinner for the sake of reduction in weight, external force for bending it by readjustment of the pointer deformed the pointer board itself or loaded it so strongly that it had influences on the main part of the tuner.